An electric-discharge machining device performs machining with respect to a workpiece by generating arc discharge in an electrode gap between a machining electrode and the workpiece. As a configuration of the electric-discharge machining device, there have been various types conventionally, with regard to a configuration of a machining power source used for generating arc discharge in the electrode gap.
Particularly, because a machining surface can be ultrafinely finished by applying a high frequency pulse to the electrode gap, a high-frequency power source device that generates a high frequency pulse has been used for a finish-machining power source, and various configuration examples have been proposed (for example, Patent Literatures 1, 2, and 3).
Patent Literature 1 describes an example of a discharge-machining power source device that applies a predetermined pulse voltage to an electrode gap between a workpiece and an electric-discharge machining electrode. The discharge-machining power source device includes a power source, a switching unit that on-off operates in a preset cycle, and an inductance element that is serially connected to the power source and the switching unit. Opposite ends of the inductance elements are electrically connected to the workpiece and the electric-discharge machining electrode. When the switching unit is turned on, because the inductance element is connected to the power source, energy is accumulated in the inductance element. When the switching unit is turned off, energy accumulated in the inductance element is supplied to the electrode gap based on a counter-induced electromotive force.
Particularly, the switching unit is formed of a switch group in which a plurality of switching units are arranged in parallel, and can reduce a load per switching element per unit time by on-off operating each switching unit in the switch group cyclically such as A→B→C→A→B . . . .
Patent Literatures 2 and 3 disclose a configuration example of a fine machining power source using a high-frequency AC power source. That is, in Patent Literature 2, a high-frequency AC power source and a work tank are connected to each other by a coaxial cable, and a matching box for matching an impedance is provided between a characteristic impedance and the work tank.
Patent Literature 3 discloses a configuration including a rough machining cable for connecting a rough-machining power source to a work tank, in addition to a finish machining cable for connecting a fine-machining power source to the work tank, and a matching circuit for adjusting the impedance in an electrode gap. Patent Literature 3 explains that a finely machined surface can be obtained by adjusting the impedance without detaching the rough machining cable.